In a gas turbine, a gas is compressed through successive stages in a compressor and mixed with fuel in a combustor The combination of gas and fuel is then ignited for generating combustion gases that are directed to turbine stages to produce rotational motion The turbine stages and compressor stages typically have stationary or non-rotary components, e.g., vanes, that cooperate with rotatable components, e.g., rotor blades, for compressing and expanding the operational gases.
Any fluid leakage between stages reduces overall gas turbine engine performance and efficiency and therefore, interstage seals are provided to reduce such leakage. In general, fluid leakage is reduced when a gap between the seal and a rotor assembly is minimized. Labyrinth seals have been used to effect a seal between stages at different pressures in gas turbine engines. Such seals generally comprise two principal elements, i e, a rotating seal and a static seal The static seal, as viewed in cross section parallel to the axial length of the engine, frequently has rows of thin labyrinth fingers or teeth, typically formed of stainless steel, extending radially from a relatively thicker base The teeth of the static seal extend radially to a location adjacent the rotating seal. If contact occurs between the labyrinth teeth and the rotating seal, the stainless steel teeth may be deformed and/or deteriorate. Accordingly, labyrinth seals have generally been designed to allow sufficient clearance to avoid problems associated with contact between the labyrinth teeth and the adjacent seal surfaces, allowing a certain amount of leakage of secondary air flow.
It is an object of the present invention to provide a seal construction for a multistage rotary machine that can avoid or minimize damage that may occur as a result of contact between the rotating seal and the stationary seal, and that maintains an adequate seal between different pressure regions defined by the engine stages.